aboutsummaryrefslogtreecommitdiff
path: root/arch/sh64/kernel/switchto.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/sh64/kernel/switchto.S')
-rw-r--r--arch/sh64/kernel/switchto.S198
1 files changed, 198 insertions, 0 deletions
diff --git a/arch/sh64/kernel/switchto.S b/arch/sh64/kernel/switchto.S
new file mode 100644
index 000000000000..45b2d90eed7d
--- /dev/null
+++ b/arch/sh64/kernel/switchto.S
@@ -0,0 +1,198 @@
+/*
+ * arch/sh64/kernel/switchto.S
+ *
+ * sh64 context switch
+ *
+ * Copyright (C) 2004 Richard Curnow
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+*/
+
+ .section .text..SHmedia32,"ax"
+ .little
+
+ .balign 32
+
+ .type sh64_switch_to,@function
+ .global sh64_switch_to
+ .global __sh64_switch_to_end
+sh64_switch_to:
+
+/* Incoming args
+ r2 - prev
+ r3 - &prev->thread
+ r4 - next
+ r5 - &next->thread
+
+ Outgoing results
+ r2 - last (=prev) : this just stays in r2 throughout
+
+ Want to create a full (struct pt_regs) on the stack to allow backtracing
+ functions to work. However, we only need to populate the callee-save
+ register slots in this structure; since we're a function our ancestors must
+ have themselves preserved all caller saved state in the stack. This saves
+ some wasted effort since we won't need to look at the values.
+
+ In particular, all caller-save registers are immediately available for
+ scratch use.
+
+*/
+
+#define FRAME_SIZE (76*8 + 8)
+
+ movi FRAME_SIZE, r0
+ sub.l r15, r0, r15
+ ! Do normal-style register save to support backtrace
+
+ st.l r15, 0, r18 ! save link reg
+ st.l r15, 4, r14 ! save fp
+ add.l r15, r63, r14 ! setup frame pointer
+
+ ! hopefully this looks normal to the backtrace now.
+
+ addi.l r15, 8, r1 ! base of pt_regs
+ addi.l r1, 24, r0 ! base of pt_regs.regs
+ addi.l r0, (63*8), r8 ! base of pt_regs.trregs
+
+ /* Note : to be fixed?
+ struct pt_regs is really designed for holding the state on entry
+ to an exception, i.e. pc,sr,regs etc. However, for the context
+ switch state, some of this is not required. But the unwinder takes
+ struct pt_regs * as an arg so we have to build this structure
+ to allow unwinding switched tasks in show_state() */
+
+ st.q r0, ( 9*8), r9
+ st.q r0, (10*8), r10
+ st.q r0, (11*8), r11
+ st.q r0, (12*8), r12
+ st.q r0, (13*8), r13
+ st.q r0, (14*8), r14 ! for unwind, want to look as though we took a trap at
+ ! the point where the process is left in suspended animation, i.e. current
+ ! fp here, not the saved one.
+ st.q r0, (16*8), r16
+
+ st.q r0, (24*8), r24
+ st.q r0, (25*8), r25
+ st.q r0, (26*8), r26
+ st.q r0, (27*8), r27
+ st.q r0, (28*8), r28
+ st.q r0, (29*8), r29
+ st.q r0, (30*8), r30
+ st.q r0, (31*8), r31
+ st.q r0, (32*8), r32
+ st.q r0, (33*8), r33
+ st.q r0, (34*8), r34
+ st.q r0, (35*8), r35
+
+ st.q r0, (44*8), r44
+ st.q r0, (45*8), r45
+ st.q r0, (46*8), r46
+ st.q r0, (47*8), r47
+ st.q r0, (48*8), r48
+ st.q r0, (49*8), r49
+ st.q r0, (50*8), r50
+ st.q r0, (51*8), r51
+ st.q r0, (52*8), r52
+ st.q r0, (53*8), r53
+ st.q r0, (54*8), r54
+ st.q r0, (55*8), r55
+ st.q r0, (56*8), r56
+ st.q r0, (57*8), r57
+ st.q r0, (58*8), r58
+ st.q r0, (59*8), r59
+
+ ! do this early as pta->gettr has no pipeline forwarding (=> 5 cycle latency)
+ ! Use a local label to avoid creating a symbol that will confuse the !
+ ! backtrace
+ pta .Lsave_pc, tr0
+
+ gettr tr5, r45
+ gettr tr6, r46
+ gettr tr7, r47
+ st.q r8, (5*8), r45
+ st.q r8, (6*8), r46
+ st.q r8, (7*8), r47
+
+ ! Now switch context
+ gettr tr0, r9
+ st.l r3, 0, r15 ! prev->thread.sp
+ st.l r3, 8, r1 ! prev->thread.kregs
+ st.l r3, 4, r9 ! prev->thread.pc
+ st.q r1, 0, r9 ! save prev->thread.pc into pt_regs->pc
+
+ ! Load PC for next task (init value or save_pc later)
+ ld.l r5, 4, r18 ! next->thread.pc
+ ! Switch stacks
+ ld.l r5, 0, r15 ! next->thread.sp
+ ptabs r18, tr0
+
+ ! Update current
+ ld.l r4, 4, r9 ! next->thread_info (2nd element of next task_struct)
+ putcon r9, kcr0 ! current = next->thread_info
+
+ ! go to save_pc for a reschedule, or the initial thread.pc for a new process
+ blink tr0, r63
+
+ ! Restore (when we come back to a previously saved task)
+.Lsave_pc:
+ addi.l r15, 32, r0 ! r0 = next's regs
+ addi.l r0, (63*8), r8 ! r8 = next's tr_regs
+
+ ld.q r8, (5*8), r45
+ ld.q r8, (6*8), r46
+ ld.q r8, (7*8), r47
+ ptabs r45, tr5
+ ptabs r46, tr6
+ ptabs r47, tr7
+
+ ld.q r0, ( 9*8), r9
+ ld.q r0, (10*8), r10
+ ld.q r0, (11*8), r11
+ ld.q r0, (12*8), r12
+ ld.q r0, (13*8), r13
+ ld.q r0, (14*8), r14
+ ld.q r0, (16*8), r16
+
+ ld.q r0, (24*8), r24
+ ld.q r0, (25*8), r25
+ ld.q r0, (26*8), r26
+ ld.q r0, (27*8), r27
+ ld.q r0, (28*8), r28
+ ld.q r0, (29*8), r29
+ ld.q r0, (30*8), r30
+ ld.q r0, (31*8), r31
+ ld.q r0, (32*8), r32
+ ld.q r0, (33*8), r33
+ ld.q r0, (34*8), r34
+ ld.q r0, (35*8), r35
+
+ ld.q r0, (44*8), r44
+ ld.q r0, (45*8), r45
+ ld.q r0, (46*8), r46
+ ld.q r0, (47*8), r47
+ ld.q r0, (48*8), r48
+ ld.q r0, (49*8), r49
+ ld.q r0, (50*8), r50
+ ld.q r0, (51*8), r51
+ ld.q r0, (52*8), r52
+ ld.q r0, (53*8), r53
+ ld.q r0, (54*8), r54
+ ld.q r0, (55*8), r55
+ ld.q r0, (56*8), r56
+ ld.q r0, (57*8), r57
+ ld.q r0, (58*8), r58
+ ld.q r0, (59*8), r59
+
+ ! epilogue
+ ld.l r15, 0, r18
+ ld.l r15, 4, r14
+ ptabs r18, tr0
+ movi FRAME_SIZE, r0
+ add r15, r0, r15
+ blink tr0, r63
+__sh64_switch_to_end:
+.LFE1:
+ .size sh64_switch_to,.LFE1-sh64_switch_to
+